Disclosed in JP-A-2003-171910 is an apparatus in which an auto fuel cock for controlling fuel feed from a fuel tank to an engine is connected to a crank case of the engine via a feed tube, and the auto fuel cock is operated by pressure pulsation generated in the crank case.
Disclosed in JP-U-61-097577 is an apparatus in which a tip of a communicating tube extended from an auto fuel cock for controlling fuel feed from a fuel tank to an engine is opened in oil accumulating at a bottom part of a crank case, and the auto fuel cock is operated by pressure pulsation generated in the crank case.
Additionally, disclosed in JP-Y-59-013336 is a apparatus in which an suction part of a fuel cock is inserted into a discharge cylinder provided on a fuel tank via an oil seal constituted by an elastic material so that the fuel cock is attached to the bottom part of the fuel tank, and in which a cylindrical lock body constituted by an elastic body fitted onto the outer circumferences of the discharge cylinder and the suction part is tightened and fixed with a fixing instrument.
In an apparatus of JP-A-2003-171910, there is a possibility that a malfunction of an auto fuel cock is caused by accumulation of oil generated by condensation of oil mist which is generated in the crank case of the engine and infiltrates into the auto fuel cock through a feed tube.
Additionally, in an apparatus of JP-U-61-097577, since a tip of a communicating tube is opened in oil accumulating at the bottom part of a crank case, there is no possibility that oil mist infiltrates into the auto fuel cock through the communicating tube. However, there is a possibility that the oil in the crank case directly infiltrates into the auto fuel cock through the communicating tube when the engine is tilted.
On the other hand, when an auto fuel cock is arranged between an engine case and a fuel tank fixed above the engine case and the inside of the engine case is connected to the auto fuel cock via a negative pressure tube, there is a problem that work for connecting a lower end of the negative pressure tube to the inside of the engine case and for connecting an upper end of the negative pressure tube to the auto fuel cock is necessary and therefore much labor and time are required for the work. In particular, the above work becomes more difficult in a case where a working space between the fuel tank and the engine case is small. The distance between the engine case and the fuel tank increases when sufficient space is ensured, and thus there exists a problem the whole engine enlarges.
Additionally, it is conceived that a negative pressure introduction joint of the auto fuel cock fixed to a lower surface of the fuel tank to a negative pressure introduction joint of the engine case via an approximate crank-shaped is a bent negative pressure tube so that the whole engine is miniaturized by shortening the distance between the engine case and the fuel tank fixed above the engine case. However, this causes a possibility that oil which infiltrates from the engine case accumulates at a bent part of the negative pressure tube when the engine is tilted. When a tip of the negative pressure introduction joint of the auto fuel cock is soaked into the oil, there is a possibility that the operation of the auto fuel cock, of which the communication with the inside of the engine case is cut off, becomes impossible.